Using charcoal for medicinal purposes has a long history (see the sidebar "Activated charcoal administration through the ages"). More recently, activated charcoal has been used to treat toxic ingestions and continues to be a form of gastrointestinal (GI) decontamination for poisoned patients—both human and animal.1,2 But now this use has largely declined in human medicine in favor of other treatment modalities (e.g. hemodialysis, plasmapheresis). In veterinary medicine, is the use of activated charcoal still appropriate?

HOW IT WORKS

Activated charcoal administration through the ages

To be effective, activated charcoal must physically come into contact with the toxicant.1 Because activated charcoal has a large surface area, it is able to adsorb many chemicals and drugs through ion-ion hydrogen binding, dipole, and van der Waals forces in the upper GI tract,3 preventing or reducing the toxicant's systemic absorption. The effectiveness of adsorption is related to molecular size and polarity of the molecules, with nonpolar compounds binding to activated charcoal well.1,3 Other factors influencing adsorption of toxicants to activated charcoal include the solubility of the poison, the presence of inorganic salts, the ionization state of the poison, the pH of the toxicant, and the presence of gastric contents.1,3

To maximize adsorption of the toxicant, activated charcoal should be administered as soon as possible after the exposure, as delayed administration can reduce its effectiveness.1 This reduction in effectiveness will vary according to the absorption rate of the toxicant ingested and overall gastric motility.

TO GIVE OR NOT TO GIVE?

The American Academy of Clinical Toxicology (AACT) and the European Association of Poisons Centres and Clinical Toxicologists (EAPCCT) created a position paper in 1997 (revised in 2004) that stated, "Single-dose activated charcoal should not be administered routinely in the management of poisoned patients... [as]... there is no evidence that administration of activated charcoal improves clinical outcome."1 Since then, the use of activated charcoal in human medicine has declined from 7.7% in 1995 to 5.9% in 2003, according to the American Association of Poison Control Centers Toxic Exposure Surveillance System.1 Despite the move in human medicine away from activated charcoal administration,1 the question of whether to continue to administer activated charcoal as part of the detoxification of poisoned patients still exists in veterinary medicine.2

Numerous studies in people and animals have evaluated activated charcoal administration and its efficacy based on the timing of ingestion. In the position paper on single-dose activated charcoal, human volunteer studies demonstrated that the effectiveness of activated charcoal administration decreased as time since exposure increased.1

Table 1 presents the results of 122 comparison studies in people that evaluated 46 drugs (e.g. acetaminophen, amiodarone, carbamazepine, fluoxetine, phenylbutazone, phenytoin, theopylline, verapamil), the absolute amount of charcoal administered (0.5 to 100 g), and the time of administration (up to 360 minutes after ingestion).1 Unfortunately, in these studies, certain factors could not be controlled, such as the influence of food in the stomach or the presence of a toxicant that may delay gastric emptying.1

Limited veterinary literature exists. Most of the animal studies were performed in mice and rats, not in dogs and cats. It is important to consider the differences in the patients' comparative anatomy, metabolism, GI motility, and morphology, as well as the toxicant's absorption rate and site, and route of elimination.1 A recent prospective study evaluated the effect of activated charcoal administration alone vs. emesis and activated charcoal administration in dogs after an experimental overdose of carprofen and found that activated charcoal administration alone was as effective as the combination was.4